MOLECULAR DYNAMICS SIMULATIONS ARE USED TO STUDY ADSORPTION OF CATIONS ON THE (010) KAOLINITE EDGE SURFACE AT AND ABOVE THE PH OF ZERO CHARGE. THE CATION SOLUTIONS ARE HIGHLY CONCENTRATED AND INCLUDE ALKALI AND ALKALINE-EARTH METALS. IT IS KNOWN THAT THE PH-DEPENDENT EDGE SURFACE OF KAOLINITE IS MORE REACTIVE THAN THE BASAL SURFACES AND MORE EAGER TO ADSORB METAL IONS; HOWEVER, KNOWLEDGE OF THE ATOMIC SCALE IS SCARCE REGARDING THE STRUCTURE OF THE SURFACE EDGE, CHARGE DISTRIBUTION, SOLVATION, AND STRUCTURE OF LAYERS OF ADSORBED CATIONS. FIRST, AB INITIO CALCULATIONS ARE USED TO DETERMINE THE ENERGETICALLY MOST FAVORABLE SURFACE TERMINATIONS AND THE DISTRIBUTION OF PARTIAL ATOMIC CHARGES ON BOTH NEUTRAL (PROTONATED) AND NEGATIVELY CHARGED (DEPROTONATED) EDGE SURFACES OF KAOLINITE. THEN, MOLECULAR DYNAMICS SIMULATIONS ARE USED TO STUDY THE SOLVATION OF KAOLINITE AND THE ADSORPTION OF CATIONS. RESULTS INCLUDE DENSITY PROFILES OF ADSORBED CATIONS, ORIENTATION PROFILES OF WATER MOLECULES CLOSE TO THE MINERAL SURFACE FOR DIFFERENT CATIONS, AND THE DISTANCE AT WHICH SUCH SURFACES BECOME NEUTRAL OR REVERSE THEIR CHARGES. RESULTS COMPARE WELL WITH AVAILABLE EXPERIMENTAL AND SIMULATION DATA. FINDINGS ARE EXPECTED TO CONTRIBUTE TO THE SELECTION OR DESIGN OF ORGANIC COMPOUNDS THAT EFFECTIVELY ADHERE TO KAOLINITE IN AQUEOUS ELECTROLYTE SOLUTIONS IN WATER RECOVERY PROCESSES.

THE MOLECULAR STRUCTURE OF THE LIQUID?VAPOR INTERFACES OF AQUEOUS SOLUTIONS OF ALKALI METAL HALIDES AND METHYL ISOBUTYL CARBINOL (MIBC, (CH3)2CHCH2COCH3) IS DETERMINED BY USING MOLECULAR DYNAMICS SIMULATIONS WITH POLARIZABLE FORCE FIELDS FOR THE FIRST TIME. THE SALTS ARE CHLORIDES, AND IODIDES, SOME OF WHICH ARE FOUND IN RAW AND PARTIALLY DESALINATED SEAWATER INCREASINGLY USED IN FLOTATION OPERATIONS IN REGIONS AFFECTED BY SEVERE AND PROLONGED DROUGHT. THE DENSITY PROFILES AT THE INTERFACES SHOW THAT ALL IONS PREFER THE INTERFACE; HOWEVER, WITH MIBC, NON-POLARIZABLE IONS, GENERALLY SMALL ONES, ARE INCREASINGLY PUSHED INTO THE LIQUID BULK. A FEW IONS OF COMPARATIVELY LESS IONIC NACL THAN KCL AND CSCL, PERSIST AT THE INTERFACE, CONSISTENT WITH SPECTROSCOPY OBSERVATIONS. ON THE OTHER HAND, STRONGLY POLARIZABLE IONS SUCH AS I? ALWAYS SHARE THE INTERFACE WITH MIBC. IN THE PRESENCE OF CHLORIDES, THE FROTHER CHAINS AT THE INTERFACE STRETCH SLIGHTLY MORE TOWARD VAPOR THAN IN FRESHWATER; HOWEVER, IN THE PRESENCE OF IODIDES, THE CHAINS STRETCH SO MUCH THAT THEY BECOME ORTHOGONAL TO THE INTERFACE, GIVING RISE TO A WELL-PACKED MONOLAYER, WHICH IS THE MOST EFFECTIVE CONFIGURATION. THE DOMINANT WATER CONFIGURATIONS AT THE INTERFACE ARE DOUBLE DONOR AND SINGLE DONOR, WITH HYDROGEN ATOMS POINTING TOWARD THE LIQUID, CONSISTENT WITH STUDIES WITH SUM-FREQUENCY GENERATION EXPERIMENTS AND EXTENSIVE AB INITIO SIMULATIONS. THIS PICTURE CHANGES RADICALLY IN THE PRESENCE OF MIBC AND SALTS. DEPENDING ON THE HALIDE AND MIBC CONCENTRATION, THE DIFFERENT MOLECULAR CONFIGURATIONS AT THE INTERFACE LEAD TO VERY DIFFERENT SURFACE TENSIONS. THE STRUCTURE AND PROPERTIES OF THESE NEW SALT-RICH INTERFACES AND THEIR IMPACT ON THE LOCATION AND ARRANGEMENT OF FROTHER MOLECULES SHOULD SERVE THE FLOTATION PRACTITIONER, ESPECIALLY IN THE SEARCH FOR THE BEST FROTHER AND DOSING IN POOR-QUALITY WATER

A COMBINATION OF THEORY AND NUMERICAL SIMULATION IS USED TO INVESTIGATE IMPURITY SUPERSTRUCTURES THAT FORM IN RAPID DIRECTIONAL SOLIDIFICATION (RDS) PROCESSES IN THE PRESENCE OF A TEMPERATURE GRADIENT AND A PULLING VELOCITY WITH AN OSCILLATORY COMPONENT. BASED ON A CAPILLARY WAVE MODEL, WE SHOW THAT THE RDS PROCESSES ARE ASSOCIATED WITH A RICH MORPHOLOGY OF BANDED STRUCTURES, INCLUDING FREQUENCY LOCKING AND THE TRANSITION TO CHAOS.

THE CRYSTAL GROWTH KINETICS AND INTERFACIAL PROPERTIES OF TITANIUM (TI) ARE STUDIED USING MOLECULAR DYNAMICS COMPUTER SIMULATION. THE INTERACTIONS BETWEEN THE TI ATOMS ARE MODELED VIA AN EMBEDDED ATOM METHOD POTENTIAL. FIRST, THE FREE SOLIDIFICATION METHOD (FSM) IS USED TO DETERMINE THE MELTING TEMPERATURE TM AT ZERO PRESSURE WHERE THE TRANSITION FROM LIQUID TO BODY-CENTERED CUBIC CRYSTAL OCCURS. FROM THE SIMULATIONS WITH THE FSM, THE KINETIC GROWTH COEFFICIENTS ARE ALSO DETERMINED FOR DIFFERENT ORIENTATIONS OF THE CRYSTAL, ANALYZING HOW THE COUPLING TO THE THERMOSTAT AFFECTS THE ESTIMATES OF THE GROWTH COEFFICIENTS. AT TM, ANISOTROPIC INTERFACIAL STIFFNESSES AND FREE ENERGIES AS WELL AS KINETIC GROWTH COEFFICIENTS ARE DETERMINED FROM CAPILLARY WAVE FLUCTUATIONS. THE SO-OBTAINED GROWTH COEFFICIENTS FROM EQUILIBRIUM FLUCTUATIONS AND WITHOUT THE COUPLING OF THE SYSTEM TO A THERMOSTAT AGREE WELL WITH THOSE EXTRACTED FROM THE FSM CALCULATIONS.

WE COMPARE EXPERIMENTAL RESULTS FROM A QUASI-TWO-DIMENSIONAL COLLOIDAL HARD SPHERE FLUID TO A MONTE CARLO SIMULATION OF HARD DISKS WITH SMALL PARTICLE DISPLACEMENTS. THE EXPERIMENTAL SHORT-TIME SELF-DIFFUSION COEFFICIENT D(S) SCALED BY THE DIFFUSION COEFFICIENT AT INFINITE DILUTION, D(0), STRONGLY DEPENDS ON THE AREA FRACTION, POINTING TO SIGNIFICANT HYDRODYNAMIC INTERACTIONS AT SHORT TIMES IN THE EXPERIMENT, WHICH ARE ABSENT IN THE SIMULATION. IN CONTRAST, THE AREA FRACTION DEPENDENCE OF THE EXPERIMENTAL LONG-TIME SELF-DIFFUSION COEFFICIENT D(L)/D(0) IS IN QUANTITATIVE AGREEMENT WITH D(L)/D(0) OBTAINED FROM THE SIMULATION. THIS INDICATES THAT THE REDUCTION IN THE PARTICLE MOBILITY AT SHORT TIMES DUE TO HYDRODYNAMIC INTERACTIONS DOES NOT LEAD TO A PROPORTIONAL REDUCTION IN THE LONG-TIME SELF-DIFFUSION COEFFICIENT. FURTHERMORE, THE QUANTITATIVE AGREEMENT BETWEEN EXPERIMENT AND SIMULATION AT LONG TIMES INDICATES THAT HYDRODYNAMIC INTERACTIONS EFFECTIVELY DO NOT AFFECT THE DEPENDENCE OF D(L)/D(0) ON THE AREA FRACTION. IN LIGHT OF THIS, WE DISCUSS THE LINK BETWEEN STRUCTURE AND LONG-TIME SELF-DIFFUSION IN TERMS OF A CONFIGURATIONAL EXCESS ENTROPY AND DO NOT FIND A SIMPLE EXPONENTIAL RELATION BETWEEN THESE QUANTITIES FOR ALL FLUID AREA FRACTIONS.

A MONTE CARLO (MC) ALGORITHM TO GENERATE PORE NETWORKS WITH SPATIAL CORRELATION OF PORE SIZES IS DEVELOPED. THE ALGORITHM IS ILLUSTRATED FOR MODEL POROUS MEDIA DESCRIBED AS A TWO-DIMENSIONAL SQUARE LATTICES OF NODES AND BONDS WHICH REPRESENT PORE BODIES AND PORE THROATS, RESPECTIVELY. WE SEEK A SPATIAL REARRANGEMENT OF PORE THROATS THAT MINIMIZES THE DIFFERENCE BETWEEN THE SEMIVARIOGRAM OF THE NETWORK AND A GIVEN MODEL SEMIVARIOGRAM. THE SPATIAL CORRELATION OF THE INITIALLY UNCORRELATED NETWORK INCREASES BY MEANS OF MC MOVES WHERE THE DIAMETERS OF A PAIR OF RANDOMLY CHOSEN PORES ARE INTERCHANGED. THE ALGORITHM PRESERVES THE INITIAL PORE SIZE DISTRIBUTION. FINALLY, THE CORRELATED PORE THROAT NETWORKS ARE USED TO DERIVE CORRELATED PORE BODY NETWORKS ONCE A GIVEN BODY-TO-THROAT SIZE RATIO IS SET. A SIMPLE PARALLEL IMPLEMENTATION OF THE ALGORITHM IS PRESENTED.

MOLECULAR DYNAMICS SIMULATIONS ARE USED TO DETERMINE THE PROPERTIES OF THE CRYSTAL?LIQUID INTERFACES OF NI AND NI50AL50. THE INTERFACIAL FREE ENERGIES AND KINETIC GROWTH COEFFICIENTS FOR DIFFERENT CRYSTAL ORIENTATIONS ARE ESTIMATED USING SIMULATIONS OF CRYSTAL?LIQUID SYSTEMS AT THE MELTING TEMPERATURE TM FROM TIME- AND WAVENUMBER-DEPENDENT CAPILLARY WAVE HEIGHT?HEIGHT CORRELATION FUNCTIONS. GROWTH COEFFICIENTS ARE ALSO DETERMINED FROM NON-EQUILIBRIUM SIMULATIONS USING THE FREE SOLIDIFICATION METHOD, WHICH COMPARES WELL WITH THOSE OBTAINED FROM ANALYSIS OF CAPILLARY WAVE FLUCTUATIONS. CRYSTAL GROWTH IN PURE NI IS ABOUT A FACTOR OF 10 FASTER THAN IN THE BINARY NI50AL50 SYSTEM. THE INTERFACIAL PROPERTIES OF THE B2 INTERMETALLIC CRYSTAL PHASE OF NI50AL50 EXHIBIT MUCH LOWER ANISOTROPY THAN THOSE OF THE FACE-CENTERED CUBIC CRYSTALLINE STRUCTURE OF NI.

A REVISED STUDY OF THE GROWTH AND MELTING OF CRYSTALS IN CONGRUENTLY MELTING AL50NI50 ALLOY IS CARRIED OUT BY MOLECULAR DYNAMICS (MDS) AND PHASE FIELD (PF) METHODS. AN EMBEDDED ATOM METHOD (EAM) POTENTIAL OF PURJA PUN AND MISHIN (2009 PHIL. MAG. 89 3245) IS USED TO ESTIMATE THE MATERIAL?S PROPERTIES (DENSITY, ENTHALPY, AND SELF-DIFFUSION) OF THE B2 CRYSTALLINE AND LIQUID PHASES OF THE ALLOY. USING THE SAME EAM POTENTIAL, THE MELTING TEMPERATURE, DENSITY, AND DIFFUSION COEFFICIENT BECOME WELL COMPARABLE WITH EXPERIMENTAL DATA IN CONTRAST WITH PREVIOUS WORKS WHERE OTHER POTENTIALS WERE USED. IN THE NEW REVISION OF MD DATA, THE KINETICS OF MELTING AND SOLIDIFICATION ARE QUANTITATIVELY EVALUATED BY THE ?CRYSTAL-LIQUID INTERFACE VELOCITY?UNDERCOOLING? RELATIONSHIP EXHIBITING THE WELL-KNOWN BELL-SHAPED KINETIC CURVE. THE TRAVELING WAVE SOLUTION OF THE KINETIC PF MODEL AS WELL AS THE HODOGRAPH EQUATION OF THE SOLID-LIQUID INTERFACE QUANTITATIVELY DESCRIBE THE ?VELOCITY?UNDERCOOLING? RELATIONSHIP OBTAINED IN THE MD SIMULATION IN THE WHOLE RANGE OF INVESTIGATED TEMPERATURES FOR MELTING AND GROWTH OF AL50NI50 CRYSTALS.

MOLECULAR DYNAMICS SIMULATIONS ALLOW DETERMINATION OF THE FORCE BETWEEN A TIP AND A SAMPLE MEDIATED BY A FLUID OR A NANOSCALE CAPILLARY BRIDGE AT ANY SEPARATION DISTANCE IN APPROACH?RETRACT CYCLES. HOWEVER, WITHOUT FURTHER CONSIDERATION, THE PROCEDURE LEADS TO FORCE?DISTANCE CURVES WITHOUT CONTROL OF TIP-TO-SAMPLE DISTANCE AND TIP OSCILLATIONS. HERE WE SHOW THAT THE SOLUTION OF A MACROSCOPIC MODEL DESCRIBING THE DYNAMICS OF THE TIP?SAMPLE INTERACTION CAN PRECISELY GUIDE THE CHOICE OF OPTIMUM PARAMETERS, FOR INSTANCE, TIP ELASTIC CONSTANT AND APPROACH SPEED, FOR CONTROLLED SIMULATIONS. THE METHOD IS APPLIED TO THE INTERACTION BETWEEN TWO SUBSTRATES IN TWO CASES OF INTERVENING FLUID: A WATER BRIDGE AND A LENNARD-JONES BRIDGE. THE METHOD CAN BE VERY USEFUL IN THE DETERMINATION OF FORCE?DISTANCE CURVES IN MORE COMPLEX SYSTEMS.

QUARTZ AND CORUNDUM SURFACES IN WATER ARE CAPABLE OF ADSORBING AND RELEASING PROTONS, A BEHAVIOR ATTRIBUTED TO THE AMPHOTERIC CHARACTER OF THEIR SILANOL AND AB INITIO CALCULATIONS ARE USED TO OBTAIN DIFFERENT CHARGE DENSITIES ON CRYSTALLINE (101) QUARTZ AND (001) CORUNDUM SURFACES AND THE CORRESPONDING CHARGE DELOCALIZATION AFTER DEPROTONATION OF THE SILANOL AND ALUMINOL GROUPS, RESPECTIVELY. THEN, CLASSICAL MOLECULAR DYNAMICS SIMULATIONS ARE USED TO STUDY THE INTERACTION OF WATER WITH THE CHARGED QUARTZ AND CORUNDUM SURFACES IN THE PRESENCE OF AQUEOUS SOLUTIONS OF MONOVALENT ALKALI AND ALKALINE-EARTH METAL CHLORIDES. RESULTS INCLUDE DENSITY PROFILES OF ADSORBED CATIONS, AND THE EFFECT OF CATIONS ON THE ORIENTATION PROFILES OF WATER MOLECULES CLOSE TO THE MINERAL SURFACES AND THE DISTANCE AT WHICH SUCH SURFACES BECOME NEUTRAL OR REVERSE THEIR CHARGES. IN ALL CASES WHERE THERE ARE EXPERIMENTAL OR SIMULATION DATA, THE RESULTS HERE COMPARE VERY WELL. THE ADSORPTION DENSITY OF CATIONS ON QUARTZ INCREASES WITH THE SIZE OF THE CATIONS, EITHER MONOVALENT OR DIVALENT. THE DENSITY OF ADSORBED MONOVALENT CATIONS ON CORUNDUM DECREASES FOR LARGER CATION SIZES, WHILE THIS BEHAVIOR ON QUARTZ IS THE OPPOSITE. IN BOTH CASES THE ADSORPTION OF CATIONS IS ENHANCED BY THE INCREASE OF THE SURFACE CHARGE. ADSORPTION ON CORUNDUM IS MUCH MORE EXTENSIVE COMPARED TO THAT ON QUARTZ FOR ALL SURFACE CHARGES AND CATIONS. THE SEQUENCE OF SIMULATIONS OF CATION ADSORPTION ON SILICA AND ALUMINA PROVIDE SUPPORT TO THE IDEA THAT HIGH ISOELECTRIC POINT MATERIALS PREFERENTIALLY ADSORB WELL-HYDRATED CATIONS AND LOW ISOELECTRIC POINT MATERIALS PREFERENTIALLY ADSORB POORLY HYDRATED CATIONS. THE RESULTS OF THIS WORK ARE EXPECTED TO CONTRIBUTE TO IMPROVING CURRENT KNOWLEDGE ON THE INTERACTION OF MINERAL OXIDES WITH MACROMOLECULES, SUCH AS POLYELECTROLYTES IN SOLID?LIQUID SEPARATION PROCESSES AND BIOMOLECULES IN LUNG INFLAMMATORY PROCESSES.

THE IMPACT OF SALTS ON PARTIALLY HYDROLYZED POLYACRYLAMIDE (HPAM) IS OF GREAT INTEREST IN MINERAL PROCESSING, CONSIDERING THAT THE USE OF SEAWATER SEEMS TO BE THE ONLY SUSTAINABLE SOLUTION IN REGIONS WITH SEVERE ARIDITY. HERE THE CONFORMATION AND TRANSPORT OF AN HPAM CHAIN IN SEVERAL SALINE SOLUTIONS ARE STUDIED BY MEANS OF MOLECULAR DYNAMICS SIMULATIONS. RESULTS INDICATE THAT THE ELECTROSTATIC REPULSION BETWEEN ANIONIC ACRYLATE UNITS CAUSES THE POLYMER TO ADOPT DIVERSE AND COMPLEX EXPANDED TERTIARY CONFORMATIONS, HOWEVER IN THE PRESENCE OF CATIONS THIS REPULSION IS SHIELDED CAUSING THE POLYMER TO FOLD INTO BALLED-UP CONFORMATIONS. THE STRUCTURE ASSUMED BY THE HPAM CHAIN DEPENDS SLIGHTLY ON THE TYPE OF CATION AND MUCH ON INTRAMOLECULAR CROSSLINKING. CATIONS INFLUENCE THE ORDERING OF WATER STRUCTURE AND ORIENTATION OF WATER DIPOLES REDUCING THE MOBILITY OF WATER, IONS, AND HPAM. THESE RESULTS ARE EXPECTED TO CONTRIBUTE TO A BETTER UNDERSTANDING OF PARTICLE FLOCCULATION FOR SUSTAINABLE WATER MANAGEMENT.

THE OSCILLATORY GROWTH OF A DILUTE BINARY ALLOY IN RAPID DIRECTIONAL SOLIDIFICATION HAS RECENTLY BEEN DESCRIBED BY A NONLINEAR OSCILLATOR EQUATION, ASSUMING A UNIFORM DIFFUSION CONSTANT OF THE SOLUTE COMPONENT IN BOTH PHASES. IN A MORE REALISTIC MODEL WITH A VANISHING DIFFUSION COEFFICIENT IN THE SOLID PHASE THIS LEADS TO THE FORMATION OF DURABLE LAYERS OF ALTERNATING SOLUTE CONCENTRATIONS. DUE TO THE MULLINS?SEKERKA INSTABILITY, THE HIGH-CONCENTRATION LAYERS COMMONLY FEATURE A DENDRITIC MICROSTRUCTURE. WE CONJECTURE THAT THE MECHANISM BEHIND THIS SO-CALLED BANDED-STRUCTURE EFFECT ALSO APPLIES TO SOME OF THE QUITE INDEPENDENTLY DISCUSSED STRIATION PHENOMENA IN A LARGE NUMBER OF GENERAL CRYSTAL-GROWTH PROCESSES.

THE ADSORPTION OF PARTIALLY HYDROLYZED POLYACRYLAMIDE (HPAM) ON QUARTZ PLAYS A KEY ROLE IN SOLID-LIQUID SEPARATION PROCESSES THAT SEEK TO RECOVER WATER FOR PROCESSING. IN THIS WORK, COMPUTATIONAL MOLECULAR DYNAMICS IS USED TO STUDY THE WATER-QUARTZ INTERFACE IN THE PRESENCE OF HPAM UNDER CONDITIONS OF HIGH SALT AND WIDE PH RANGE. THE SALTS USED ARE MOSTLY THOSE OF SEAWATER. SMALL WATER-STRUCTURE MAKER CATIONS ARE PREFERENTIALLY ADSORBED ONTO THE POLYMER RATHER THAN ONTO THE QUARTZ SURFACES. IN FRESHWATER, THE ADSORPTION OF HPAM ON QUARTZ IS REDUCED TO VERY FEW CONTACTS, HOWEVER IN SALTWATER THE ADSORPTION CONTACTS OF HPAM INCREASE ALTHOUGH DECREASE WITH SURFACE CHARGE, MAINLY DUE TO ELECTROSTATIC REPULSION. IN THE PRESENCE OF MONOVALENT CATIONS AND FOR ANY SURFACE CHARGE ON THE QUARTZ, ABOVE THE ISOELECTRIC POINT, THE ADSORPTION CONTACTS OF HPAM DECREASES AS THE CATION SIZE INCREASES, WHICH IS EXPECTED CONSIDERING THAT SMALLER CATIONS ARE MORE EFFECTIVE IN NEUTRALIZING BOTH QUARTZ AND HPAM. THE RESULTS SHOW THAT THE ADSORPTION OF HPAM OCCURS EXCLUSIVELY VIA SALT BRIDGES. ONE WAY OF DESCRIBING THE CONFORMATION OF AN HPAM CHAIN ADSORBED ONTO QUARTZ IS TO REDUCE IT TO THE SKELETON OF CARBON ATOMS OF THE POLYMER CHAIN AND THEN DETERMINE THE FRACTION OF THESE ATOMS IN LOOPS, TRAINS, AND TAILS. IN GENERAL, THE ADSORPTION CONTACTS OF HPAM ARE FEW, THE CARBON FRACTIONS IN TRAINS AND LOOPS ARE TINY, AND THEREFORE MOST OF THE CARBON ATOMS IN HPAM REMAIN IN LONG TAILS READY TO GET ENTANGLED WITH OTHER TAILS THUS FAVORING THE FLOCCULATION PROCESS. THE RESULTS ARE EXPECTED TO CONTRIBUTE TO SUSTAINABLE WATER MANAGEMENT THROUGH THE RIGHT CHOICE OF FLOCCULANT BASED ON MOLECULAR ASPECTS.

THE FINITE PARTICLE METHOD (FPM) AND THE DECOUPLED FINITE PARTICLE METHOD (DFPM) ARE VARIANTS OF THE SMOOTHED PARTICLE HYDRODYNAMICS (SPH) IN WHICH THE ESTIMATION OF A FIELD AND ITS GRADIENT FOR AN ARBITRARY DISTRIBUTION OF PARTICLES IS PERFORMED BY IMPOSING FIRST ORDER CONSISTENCY EQUATIONS (). A MODIFICATION OF THE KERNEL IS INTRODUCED THAT INVOLVES THE INVERSION OF A CORRECTION MATRIX FOR EACH INTERPOLATION POINT IN THE SYSTEM. IN THE FPM, THE INVERSION IS RIGOROUSLY PERFORMED AND THEREFORE THE METHOD HAS FIRST-ORDER CONSISTENCY (). HOWEVER, IN DPFM THE VANISHINGLY SMALL NON-DIAGONAL TERMS IN THE CORRECTION MATRIX ARE NEGLECTED TO OBTAIN A MORE STRAIGHTFORWARD METHOD, AT EXPENSE OF CONSISTENCY. FOLLOWING THE IDEA OF DFPM, THE SEMI-DECOUPLED FINITE PARTICLE METHOD (SDFPM) AND THE CORRECTED SEMI DECOUPLED FINITE PARTICLE METHOD (CSDFPM) ARE INTRODUCED. IN THE SDFPM, THE KERNEL IS NORMALIZED BY A SHEPARD FACTOR AND THE FIRST ORDER CONSISTENCY EQUATIONS ARE SOLVED BY NEGLECTING NON-DIAGONAL TERMS IN THE CORRECTION MATRIX AS IN THE DFPM METHOD. IN THE CORRECTED VERSION OF THIS METHOD (CSDFPM), THE SDFPM ESTIMATION IS USED AS THE INITIAL GUESS TO GET A SECOND CORRECTED ESTIMATION IN THE EQUATIONS. THE PRECISION OF FPM, DFPM, SDFPM, AND CSDFPM IS TESTED BY EVALUATING THE GRADIENT COMPONENTS OF A FIELD AROUND A CYLINDRICAL OBSTACLE AND AROUND A CYLINDRICAL HOLE BY USING (I) TRIAL FIELD FUNCTIONS WITH AN ORDERED ARRAY OF PARTICLES AND (II) THE PRESSURE FIELD WITH A DISTRIBUTION OF PARTICLES TAKEN FROM A FLOW SIMULATION. DRAG COEFFICIENTS FOR FLOW AROUND A CYLINDER ARE OBTAINED BY THE DIFFERENT METHODS AND COMPARED IN A WIDE RANGE OF REYNOLDS NUMBERS, INCLUDING THE LAMINAR AND TURBULENT REGIMES. THE GRADIENT COMPONENTS AND DRAG COEFFICIENTS CALCULATED WITH THE PROPOSED METHODS SHOW A PRECISION COMPARABLE TO THE FPM AT A LOWER COMPUTATIONAL COST.

METHYL ISOBUTYL CARBINOL (MIBC) IS A HIGH-PERFORMANCE SURFACTANT WITH UNUSUAL INTERFACIAL PROPERTIES MUCH APPRECIATED IN INDUSTRIAL APPLICATIONS, PARTICULARLY IN MINERAL FLOTATION. IN THIS STUDY, THE STRUCTURE OF AIR?LIQUID INTERFACES OF AQUEOUS SOLUTIONS OF MIBC-NACL IS DETERMINED BY USING MOLECULAR DYNAMICS SIMULATIONS EMPLOYING POLARIZABLE AND NONPOLARIZABLE FORCE FIELDS. DENSITY PROFILES AT THE INTERFACES AND SURFACE TENSION FOR A WIDE RANGE OF MIBC CONCENTRATIONS REVEAL THE KEY ROLE OF POLARIZABILITY IN DETERMINING THE SURFACE SOLVATION OF CL? IONS AND THE EXPULSION OF NON-POLARIZABLE NA+ IONS FROM THE INTERFACE TO THE LIQUID BULK, IN AGREEMENT WITH SPECTROSCOPIC EXPERIMENTS. THE ORIENTATION OF MIBC MOLECULES AT THE WATER LIQUID?VAPOR INTERFACE CHANGES AS THE CONCENTRATION OF MIBC INCREASES, FROM PARALLEL TO THE INTERFACE TO PERPENDICULAR, LEADING TO A WELL-PACKED MONOLAYER. SURFACE TENSION CURVES OF FRESH WATER AND AQUEOUS NACL SOLUTIONS IN THE PRESENCE OF MIBC INTERSECT AT A REPRODUCIBLE SURFACTANT CONCENTRATION FOR A WIDE RANGE OF SALT CONCENTRATIONS. THE SIMULATION RESULTS FOR A 1 M NACL AQUEOUS SOLUTION WITH POLARIZABLE WATER AND IONS CLOSELY CAPTURE THE MIBC CONCENTRATION AT THE INTERCEPT. THE INCREASE IN SURFACE TENSION OF THE AQUEOUS MIBC/NACL MIXTURE BELOW THE CONCENTRATION OF MIBC AT THE INTERSECTION SEEMS TO ORIGINATE IN A DISTURBANCE OF THE INTERFACIAL HYDROGEN BONDING STRUCTURE OF THE SURFACE LIQUID WATER CAUSED BY NA+ IONS ACTING AT A DISTANCE AND NOT BY ITS PRESENCE ON THE INTERFACE.